<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        /* 类选择器 */
/* .one{
    background-color: red;
}.two{
    background-color: yellow;
} */
 /* 后代选择器 */
 /* div button{
    background-color: yellow;
 } */
  /* 悬停 伪类选择器 */
  button:hover{
    background-color: red;
    width: 100px ;
    /* 鼠标图标 */
    cursor: pointer;
  }
  /* 被点击  */
  button:active{
    background-color: yellow;
  }
    </style>
</head>
<body>
    <!-- <div class="one">div1</div>
    <div class="two">div2</div>
    <div><button>普通的按钮</button></div>
    <button>按钮</button> -->
    <button>登录</button>
</body>
</html>